Not commenting on this specific case, but it is possible for things held (or not) by pilots to affect the controls. An RAF Voyager (strategic lift aircraft based on the A330) dived 4000ft because the pilot was using a personal camera throughout the flight and it got stuck between his seat and the joystick, and his failure to admit it caused an accident investigation that temporarily grounded the entire fleet [0], [1].
> Investigators from the National Transportation Safety Board (NTSB) have demonstrated that an Apple iPad likely jammed against the co-pilot’s left pedal prior to the fatal crash of a Rotak Helicopter Services Chinook in Idaho last year.
It's also happened to me once that something was dropped and got wedged behind the rudder pedal, blocking its movement. Tiny GA aircraft and we noticed it during the start-up check (when you check the full range of the flight controls). The checklist did its job. But if it had dropped during flight it could have been really dangerous.
I can imagine it can happen even in more professional circles.
True, good point. But it's very very hard to do that on an aircraft because space is at a huge premium. You simply don't have infinite space around the pedals. Or other controls for that matter. For example a clipboard could fall on the center pedestal and flip one of the gazillion switches. Luckily most important ones have barriers around them, or other safeguards like the need to lift up the lever before moving it.
[0] https://www.independent.co.uk/news/uk/home-news/revealed-raf...
[1] https://www.bbc.co.uk/news/uk-england-39153163